Hydraulically actuated fabric seal with pull-down and push-out mechanism



July 11, 1961 J. H. WIGGINS 2,991,901

HYDRAULICALLY ACTUATED FABRIC SEAL WITH PULL-DOWN AND PUSH-OUT MECHANISMS 3 Sheets-Sheet 1 Filed July 10, 1959 FIG.

JNVENTOR. JOHN H. W/GG/NS W A? 79 ATTORNEYS July 11, 1961 J. H. WIGGINS 2,991,901

HYDRAULICALLY ACTUATED FABRIC SEAL WITH PULLDOWN AND PUSH-OUT MECHANISMS Filed July 10, 1959 3 Sheets-Sheet 2 INVENTOR. JOHN H. W/GG/NS BY 044 4. @44 c12 2- W be 7 ATTORNEYS y 1961 J H WIGGINS 2,991,901

HYDRAULICALLY ACTUATED FABRIC SEAL WITH PULLDOWN AND PUSH-OUT MECHANISMS Filed July 10, 1959 3 Sheets-Sheet 3 INVENTOR. JOHN H. W/GG/NS J ATTORNEYS United tates Patent Ofiie 2,991,901 Patented July 11, 1961 2 991,901 HYDRAULICALLY ACTUATED FA'BRIC SEAL WITH PULL-DOWN AND PUSH-OUT lVIECH- ANISMS John H. Wiggins, 801C El Camino Real, Menlo Park, Calif. Filed July 10, 1959, Ser. No. 826,176 9 Claims. (Cl. 220-26) This invention relates to sealing mechanisms in a cylindrical storage tank for petroleum products, and the like, of the type having a floating roof, and is concerned more particularly with this type of sealing mechanism wherein the seal is suspended or supported on the floating roof to extend into the liquid in the tank and also to contact the side wall of the tank so as to minimize evaporation losses.

It is a general object of the invention to provide an improved sealing mechanism between the side wall and the floating roof of a storage tank for petroleum products and the like. Another object of the invention is to provide a sealing mechanism of the above type which is of the so-called wet type so as to be hydraulically actuated in its sealing action.

A further object of the invention is to provide a sealing mechanism of the above character which is provided with automatically operable means to push the seal out toward the wall of the tank and maintain it in good sealing condition.

Still another object of the invention is to provide sealing mechanism of the above character in which means is provided to break any adherence between the wall and the seal which would interfere with free movement of the seal in response to changes of level of liquid in the tank.

A still further object of the invention is to provide sealing means of the above character in which the seal includes means to prevent capillary lift between the seal and the wall so that loss of liquid from this cause is minimized.

Still another object of the invent-ion is to provide improved sealing means of the above character which is provided with means to insure a desired vertical distance of contact with the seal with the cylindrical tank wall.

Still another object of the invention is to provide a sealing mechanism of the above character in which the area of contact with the wall is made at least in part by a reinforced structure so as to insure long life.

A still further object of the invention is to provide a sealing mechanism of the above character constructed so that no explosive gas pockets can form or collect between the sealing mechanism and the surface of the stored liquid.

Other objects and advantages of the invention will be apparent from the following description of a preferred embodiment thereof, as disclosed in the accompanying description, taken in conjunction with the attached drawings, in which:

FIGURE 1 is a fragmentary vertical sectional view through a storage tank of the floating roof type incorporating the invention as the floating roof floats on the stored liquid. In this figure the full line position of parts shows the widest possible separation of the floating roof from the side wall of the tank, and the dotted line position of the floating roof is at its closest position to the side wall.

FIGURE 2 is a view similar to FIGURE 1 and illustrating the sealing mechanism with a normal gap between the cylindrical side wall of the tank and the side of the floating roof as positioned when the roof and sealing mechani m are ascending FIGURE 3 is another view similar to FIGURE 2 but illustrating another condition of the parts.

FIGURE 4 is a fragmentary elevational view taken in a plane indicated by the line 44 in FIGURE 1 passing through the sealing mechanism and looking toward the wall of the cylindrical tank, the view being shown as a developed view rather than as a true sectional elevation.

FIGURE 5 is a view similar to FIGURE 4 but illustrating a modified form of the invention.

FIGURE 6 is a sectional view similar to FIGURE 2 illustrating the modified form of the invention.

Referring to FIGURES l and 4 there is shown a storage tank for petroleum products or the like having a cylindrical upright side wall 10 and a bottom wall 11. Within the cylindrical side wall 10 there is provided a roof of the floating type having an outer pontoon 12 of circular outline which occupies the outer fraction of the area of the tank, and is connected to a plate-like deck 13 which may cover the remainder of the surface area of the tank, a center pontoon sometimes also being provided. In this type of tank such as used for storing petroleum products, for example, the liquid level 14 of the tank is expected to rise and fall from time to time as the tank fills and empties and the roof of the present invention is designed to float on the liquid and to rise and to fall with the changes in liquid level. When stor age of volatile liquids is contemplated, it is important that there be no escape of this liquid by volatilization and that there be no explosive gases trapped in the gap between the floating roof and the tank wall and it is for this purpose that the sealing mechanism as disclosed herein is provided.

The sealing mechanism of the instant invention is designed to prevent any space above the stored liquid which can trap an explosive mixture of air and vapor, and preferably comprises a hydraulically actuated or wet fabric seal which forms a downward loop between the rim 15 and the wall 10 and extends down into the liquid, and the fabric is attached to a side portion or of the floating roof and contacts the side wall at respective points which are below-the liquid level in the tank. Means are provided within the seal to actuate the seal to insure positive and maximum vertical contact between the seal fabric and the tank wall, and to control the positioning of the seal fabric during the two sliding movements of the fabric relative to the side wall--the upward movement and the downward movement-as the roof moves vertically in response to changes in liquid level in the tank.

Referring to FIGURES 1 and 3, the sealing mechanism comprises generally an annular fabric 16 which has an upper line of attachment at one edge around the upper portion of the roof pontoon 12, and at the lower edge portion thereof a lower line of attachment around the pontoon 12 so as to drape in proper fashion with refer-. ence to the outer wall 10 and the roof 12 and to provide a looped portion which when hydraulically actuated occupies the gap between the roof and the side wall and extends below the liquid level 14 of the tank as stated above. As seen in FIGURE 1, the upper edge portion of the fabric seal 16 is clamped between an angle 17 secured as by welding about the outer pontoon 12 adja cent to the upper edge thereof and extending radially. outward to engage the fabric seal 16, and a circular seal bar 18 secured in place by a plurality of fastening bolts 19. Also as seen in FIGURE 1, the lower edge portion is clamped between a peripheral angle 21 secured as by welding about the periphery of the pontoon 12 at approximately the level of stored liquid of the tank, and a lower seal .bar 22 which is secured and clamped in place by bolts 23.

It will be noted that the fabric seal 16, and the POE- toon 12 form an annular chamber to hold the hydraulic seal actuating liquid 24 which urges the looped portion of the seal 16 yieldably against the side wall 10.

Means is provided for absorbing the major portion of localized extra heavy wear on the seal 16, and this means comprises an annular wear or scuff band 31 of fabric and rubber, which is vulcanized to the fabric seal, and is provided with a tapered upper end portion 31a. The wear band 31 may be a series of segments but preferably extends continuously about the fabric seal at the location immediately above the liquid level 30 of the hydraulic actuating fluid 24 for the seal. This wear band 31 may also be made of steel plates or a steel strip.

This annular wear band 31 has incorporated therein a means for preventing loss of liquid by capillary action in creeping up between the fabric seal 16 and side wall 10 of the tank; and this means for breaking the capillary lift, comprises a recessed lower portion 32 extending about the entire lower periphery of the wear band 31 and providing an annular recess 33 therein which is of suflicient width and height as to be several times the effective spacing for stopping capillary action.

Means are provided within the sealing chamber for the hydraulic actuating fluid for pressing an upper portion of the fabric seal yieldably against the side wall 10 of the tank. This means may comprise an annular series of spring members 36 (FIGURES l and 4) which are secured at their upper ends between the seal bar 18 and the angle 17, and which extend downwardly and inwardly and then downwardly and outwardly, being provided at their lower ends with an outwardly extending portion 36a which contacts the seal 16 behind the wear band 31. As shown in FIGURE 1 the seal contacting portion 36a has its end curved to present a smooth enlarged surface to the seal 16. In this connection, if desired, the wear strip 31 may comprise a segmental annular series of members, the wear strips coinciding with the spring members 36 and 36a which may be spaced, for example, from two to four feet apart about the periphery of the storage tank.

If desired, the spring members 36 (FIGURES and 6) may be provided with transverse rods 37 having respective enlarged portions 38 of synthetic rubber or steel for engaging and urging the fabric seal 16 toward the side wall, thus reducing the unit pressure and distributing the pressure substantially continuously around.

It will be noted that this auxiliary means for urging the fabric out toward the tank wall also tends to hold the floating roof in the tank center, as well as increasing the height of the contact area between the fabric of the seal and the wall of the tank.

The sealing mechanism also includes means for causing the fabric seal to move down with the floating roof when such action occurs, in effect pulling the fabric down at a lower portion thereof, if it should adhere to the tank wall by reason of friction or freezing. This. means comprises an annular series of substantially U-shaped stays 41 (FIGURES 1 and 4), having their respective upper ends bent at 41a to pivotally engage in brackets 42 attached about the periphery of the pontoon 12, and having a lower horizontal portion 41b disposed within the looped portion of the fabric seal. Upon downward movement of the floating roof, the portion 41b will en gage the seal 16 as shown in FIGURE 3, and cause it to move downwardly with respect to the side wall breaking it free therefrom if any adherence is present.

If desired the loop or actuating portion 41b (FIGURES 5 and 6) of each stay 41, may be supplied with an enlarged portion 43 of resilient material or of steel to increase the area of contact and to minimize wear on the fabric seal. This enlarged portion 43 may be formed of material of less specific gravity than the specific gravity of the liquid 24 within the seal 16, and in this event will occupy the position shown in dotted lines in FIGURE 6.

The chamber formed between the fabric seal 16 and the pontoon roof 12 contains a non-explosive petroleum product, such as heavy oil, as the seal actuating liquid, but by virtue of osmosis through the rubber impregnated fabric of the fabric seal 16 certain volatile fractions may be incorporated in this petroleum during operation of the tank in storing such volatile liquid. To avoid the possibility of an explosive mixture being formed in the air space above the liquid level of the hydraulic actuating liquid in the seal, and to accommodate changes in volume of the seal as the volume varies during flexing of the fabric, vents 46 are provided in the angle 17 at the top, being spaced about the periphery of the roof and being protected from the weather by a suitable weather hood.

Referring to FIGURE 1 it will be seen that a vent pipe 47 leads from the space outside the rim 15 and below the angle '21 to the atmosphere above the floating roof 12, so that any volatile constituents which may tend to accumulate in this annular space will be vented to the atmosphere and prevent the accumulation or trapping of an explosive mixture in this annular space. A suitable number of vents 47 are provided around the periphery of the floating roof 12.

In operation of the seal, the normal position of the parts is illustrated in FIGURE 4 the full line view of the parts where the actuating liquid 24 is urging the looped portion of the seal, including the lower part of the scuff or wear band 31 against the side wall 10 of the tank. This area of contact is maintained yieldably down to the point of curvature adjacent to the bottom of the fabric seal 16. The spring members 36 are contacting the fabric seal 16 behind the scuff or wear band 31, so as to maintain a light sealing engagement at an upper part of the looped portion, the lower part of the looped portion actually entering the stored liquid in the tank 10 so as to prevent any space for accumulation of gas above the surface of the liquid.

The stays 41 normally may hang idly (or be gently held against the fabric) within the chamber formed by the fabric seal 16 and the floating roof 12. The vents 46 maintain the gas in the space above the liquid 24 below an explosive mixture in content. The recess 32 serves to break up any capillary lifting action between the tank wall 10 and the seal 16. r The condition of the parts will vary as the position of the floating roof varies with respect to the upright side wall 10, from a maximum gap spacing as shown in full lines in FIGURE 1 to a minimum gap condition as shown in dotted lines in this figure. The spring members 36 pressing outwardly against the seal 16 tend to keep the floating roof 12 centered.

As the floating roof moves upward, the fabric slides upward along the wall and friction tends to pull the fabric down. This friction plus the weight of the seal is overcome by tension in the upper part of the fabric as shown in FIG. 2. This upper fabric part slants away from the Wall and would pull a substantial area of the fabric out of contact with the wall, thereby decreasing the vertical contact of wall and fabric. The springs 36 overcome that slanted pull. The springs 36 also increase the vertical fabric-wall contact. Moreover, the springs 36 hold the entire floating roof in the geometric center of the tank.

As the roof movement changes direction the fabric must slide down the wall. Friction caused by (a) the pressure of springs 36 and (b) the hydraulic pressure of the liquid 24 inside the seal, tends to hold the fabric momentarily stationary relative to the wall. The weight of the liquid normally may not overcome the above friction until there is a downward pull exerted by the lower part of the fabric. Additionally, as an exaggerated condition, if the upper part of the seal is frozen to the wall by ice, the floating roof will have to descend so far before the lower part of the fabric pulls down, that the oil in the tank is exposed to atmosphere.

Itis readily seen that the floating roof would have to descend several inches before it is positively certain that the fabric would pull down under which conditions there would be an air space between the wall at the lower part of the fabric and the surface of the stored petroleum product, for example, gasoline, thereby creating an evaporation and fire hazard.

This is where the swingable members 41 operate. If the fabric remains stationary relative to the wall while the floating roof moves down, say 1", the horizontal runs 41a of members 41 contact the fabric 16 at the bottom of the loop, the fabric straightens between that point and the wall and quickly pushes down on the bottom of the loop of the fabric and creates a downward pull to overcome friction or in an emergency to pull the fabric quickly away from ice that may be freezing the upper part of the fabric to the wall. In order to get almost instantaneous action by swingable members 41, they may be very gently held just in contact with the lower part of the fabric by mechanical means such as springs, floats or counterweights.

Thus friction or freezing is overcome by both upward and downward movement.

The foregoing description of certain embodiments of the present invention has been made for clearness of understanding only and no unnecessary limitations are intended thereby, for it will be apparent to those skilled in the art that various modifications may be made in the present seal structure within the sphere and scope of the appended claims.

What is claimed is:

1. In a tank for storing liquids, such as petroleum products, including an upstanding substantially cylindrical side wall, and a floating roof arranged in said tank and including upstanding substantially cylindrical wall structure spaced radially inwardly from said tank side wall and defining an upstanding substantially annular space therebetween; sealing mechanism for said annular space comprising a substantially annular sealing element ar ranged in said annular space and carried by said wall structure and movable therewith with respect to said tank side Wall, said sealing element being formed of flexible sheet-like material that is highly impervious to the constituents of petroleum products, an upper annular portion of said sealing element being sealed to an upper annular portion of said wall structure and a lower annular portion of said sealing element being sealed to a lower annular portion of said wall structure and an intermediate annular portion of said sealing element being looped between said upper and lower annular portions thereof to define an annular chamber between said sealing element and the adjacent annular portion of said wall structure, a plurality of circumferentially spaced-apart resilient members carried by the upper portion of said wall structure and depending therefrom and disposed in said chamber, the lower portions of said resilient members engaging an intermediate annular sealing section of said sealing element resiliently to urge the same into sliding sealed engagement with said tank side wall, and a plurality of circumferentially spaced-apart stays carried by the intermediate portion of said wall structure and depending therefrom and disposed in said chamber, the lower portions of said stays engaging a lower annular looped section of said sealing element and maintaining the same in submerged position with respect to the liquid stored in said tank and limiting upward relative movement of said sealing element with respect to said wall structure during downward movement of said roof with respect to said tank side wall.

2. In a tank for storing liquids, such as petroleum products, including an upstanding substantially cylindrical side wall, and a floating roof arranged in said tank and including upstanding substantially cylindrical wall structure spaced radially inwardly from said tank side Wall and defining an upstanding substantially annular space therebetween; sealing mechanism for said annular space comprising a substantially annular sealing element arranged in said annular space and carried by said wall structure and movable therewith with respect to said tank side wall, said sealing element being formed of flexible sheet-like material that is highly impervious to the constituents of petroleum products, an upper annular portion of said sealing element being sealed to an upper annular portion of said wall structure and a lower annular portion of said sealing element being sealed to a lower annular portion of said wall structure and an intermediate annular portion of said sealing element being looped between said upper and lower annular portions thereof to define an annular chamber between said sealing element and the adjacent annular portion of said wall structure, a plurality of circumferentially spaced-apart resilient members carried by the upper portion of said wall structure and depending therefrom and disposed in said chamber, a plurality of rollers respectively carried by the lower portions of said resilient members and engaging an intermediate annular sealing section of said sealing element to urge tbe'same into sliding sealed engagement with said tank side wall, and a plurality of circumferentially spaced-apart stays carried by the intermediate portion of said wall structure and depending therefrom and disposed in said chamber, the lower portions of said stays engaging a lower annular looped section of said sealing element and maintaining the same in submerged position with respect to the liquid stored in said tank and limiting upward relative movement of said sealing element with respect to said wall structure during downward movement of said roof with respect to said tank side wall.

3. In a tank for storing liquids, such as petroleum products, including an upstanding substantially cylindrical side wall, and a floating roof arranged in said tank and including upstanding substantially cylindrical wall structure spaced radially inwardly from said tank side wall and defining an upstanding substantially annular space therebetween; sealing mechanism for said annular space comprising a substantially annular sealing element arranged in said annular space and carried by said wall structure and movable therewith with respect to said tank side wall, saidsealing element being formed of flexible sheet-like material that is highly impervious to the constituents of petroleum products, an upper annular portion of said sealing element being sealed to an upper annular portion of said wall structure and a lower annular portion of said sealing element being sealed to a lower annular portion of said wall structure and an intermediate annular portion of said sealing element being looped between said upper and lower annular portions thereof to define an annular chamber between said sealing element and the adjacent annular portion of said wall structure, a plurality of circumferentially spacedapart resilient members carried by the upper portion of said wall structure and depending therefrom and disposed in said chamber, the lower portions of said resilient members engaging an intermediate annular sealing section of said sealing element resiliently to urge the same into sliding sealed engagement with said tank side wall, a plurality of circumferentially spaced-apart stays carried by the intermediate portion of said wall structure and depending therefrom and disposed in said chamber, and a plurality of rollers respectively carried by the lower portions of said stays and engaging a lower annular looped section of said sealing element and maintaining the same in submerged position with respect to the liquid stored in said tank and limiting upward relative movement of said sealing element with respect to said wall structure during downward movement of said roof with respect to said tank side wall.

4. In a tank for storing liquids, such as petroleum products, including an upstanding substantially cylindrical side wall, and a floating roof arranged in said tank and including upstanding substantially cylindrical wall structure spaced radially inwardly from said tank side wall and defining an upstanding substantially annular space therebetween; sealing mechanism for said annular space comprising a substantially annular sealing clement arranged in said annular space and carried by said wall structure and movable therewith with respect to said tank side wall, said sealing element being formed of flexible sheet-like material that is highly impervious to the constituents of petroleum products, an upper annular portion of said sealing element being sealed to an upper annular portion of said wall structure and a lower annular portion of said sealing element being sealed to a lower annular portion of said wall structure and an intermediate annular portion of said sealing element being looped between said upper and lower annular portions thereof to define an annular chamber between said sealing element and the adjacent annular portion of said wall structure, a plurality of circumferentially spacedapart resilient members carried by the upper portion of said wall structure and depending therefrom and disposed in said chamber, the lower portions of said resilient members engaging an intermediate annular sealing section of said sealing element resiliently to urge the same into sliding sealed engagement with said tank side wall, a plurality of circumferentially spaced-apart stays carried by the intermediate portion of said wall structure and depending therefrom and disposed in said chamber, the lower portions of said stays engaging a lower annular looped section of said sealing element and maintaining the same in submerged position with respect to the liquid stored in said tank and limiting upward relative movement of said sealing element with respect to said wall structure during downward movement of said roof with respect to said tank side wall, and a body of sealactuating liquid contained in the lower portion of said chamber and assisting said stays in maintaining the lower annular looped section of said sealing element in submerged position with respect to the liquid stored in said tank and in limiting upward relative movement of said sealing element with respect to said wall structure during downward movement of said roof with respect to said tank side wall.

5. The sealing mechanism set forth in claim 4, and further comprising means for venting to the atmosphere the upper portion of said chamber disposed above said body of seal-actuating liquid contained therein, so as to prevent the accumulation of any volatile products in the upper portion of said chamber' 6. In a tank for storing liquids, such as petroleum products, including an upstanding substantially cylindrical side wall, and a floating roof arranged in said tank and including upstanding substantially cylindrical wall structure spaced radially inwardly from said tank side wall and defining an upstanding substantially annular space therebetween; sealing mechanism for said annular space comprising a substantially annular sealing element arranged in said annular space and carried by said wall structure and movable therewith with respect to said tank side wall, said sealing element being formed of flexible sheet-like material that is highly impervious to the constituents of petroleum products, an upper annular portion of said sealing element being sealed to an upper annular portion of said wall structure and a lower annular portion of said sealing element being sealed to a lower annular portion of said wall structure and an intermediate annular portion of said sealing element being looped between said upper and lower annular portions thereof to define an annular chamber between said sealing element and the adjacent annular portion of said wall structure, a plurality of circumferentially spaced-apart resilient members carried by the upper portion of said wall structure and depending therefrom and disposed in said chamber, the lower portions of said resilient members engaging an intermediate annular sealing section of said sealing element resiliently to urge the same into sliding sealed engagement with said tank side wall, a plurality of circumferentially spaced-apart stays respectively pivotally connected at the upper portions thereof to the intermediate portion of said wall structure and depending therefrom and disposed in said chamber, so that said stays are mounted for pivotal movements in said chamber in response to sidewise movements of said roof with respect to said tank side wall, a plurality of rollers respectively carried by the lower portions of said stays and disposed in said chamber and engaging a lower annular looped section of said sealing element and maintaining the same in submerged position with respect to the liquid stored in said tank and limiting upward relative movement of said sealing element with respect to said wall structure during downward movement of said roof with respect to said tank side wall, and a body of seal-actuating liquid contained in the lower portion of said chamber and suberging said rollers and assisting said stays in maintaining the lower annular looped section of said sealing element in submerged position with respect to the liquid stored in said tank and in limiting upward relative movement of said sealing element with respect to said wall structure during downward movement of said roof with respect to said tank side wall.

7. The sealing mechanism set forth in claim 6, wherein said seal-actuating liquid has a specific gravity that is higher than that of the material of said rollers, so that said rollers are buoyed upwardly tending to pivot said stays radially outwardly in said chamber toward said tank side wall.

8. In a tank for storing liquids, such as petroleum products, including an upstanding substantially cylindrical side wall, and a floating roof arranged in said tank and including upstanding substantially cylindrical wall structure spaced radially inwardly from said tank side wall and defining an upstanding substantially annular space there- 'between; sealing mechanism for said annular space comprising a substantially annular sealing element arranged in said annular space and carried by said wall structure and movable therewith with respect to said tank side wall, said sealing element being formed of flexible sheetlike material that is highly impervious to the constituents of petroleum products, an upper annular portion of said sealing element being sealed to an upper annular portion of said wall structure and a lower annular portion of said sealing element being sealed to a lower annular portion of said wall structure and an intermediate annular portion of said sealing element being looped between said upper and lower annular portions thereof to define an annular chamber between said sealing element and the adjacent annular portion of said wall structure, an annular scuff band carried by the outer surface of an intermediate annular section of said sealing element in facing relaticn with respect to the inner surface of said tank side wall, a plurality of circumfcrentially spaced-apart resilient members carried by the upper portion of said wall structure and depending therefrom and disposed in said chamber, the lower portions of said resilient members engaging the inner surface of the intermediate annular section of said sealing element resiliently to urge said scuff band into sliding sealed engagement with said tank side wall, and a plurality of circumferentially spaced-apart stays carried by the intermediate portion of said wall structure and depending therefrom and disposed in said chamber, the lower portions of said stays engaging a lower annular looped section of said sealing element and maintaining the same in submerged position with respect to the liquid stored in said tank and limiting upward relative movement of said sealing element with respect to said wall structure during downward movement of said roof with respect to said tank side wall.

9. The sealing mechanism set forth in claim 8, wherein said scuff band has an annular recess formed therein and disposed above the level of the liquid stored in said References Cited in the file of this patent UNITED STATES PATENTS Maker Nov. 10, 1931 Haupt et a1 Sept. 14, 1937 Boberg July 25, 1950 Goldsby et a1 Nov. 28, 1950 Goldsby et a1. Jan. 16, 1951 Fino Feb. 21, 1956 FOREIGN PATENTS Switzerland May 1, 1922 

